Christoph Herwig

TU Wien | TU Wien · Institute of Chemical Engineering

Objective Random effects are often neglected when defining the control strategy for a biopharmaceutical process. In this article, we present a case study that highlights the importance of considering the variance introduced by random effects in the calculation of proven acceptable ranges (PAR), which form the basis of the control strategy. Methods...

Highlights: • Particle filter for simultaneous estimation of yield coefficient and maximum uptake capacity based on non-invasive offgas measurements • Enhancing the parametric sensitivity by short substrate perturbations lead to better parameter estimation • Accurate estimation results on real experiments with different feed profiles • Monitor...

Statistical experimental designs such as factorial, optimal, or definitive screening designs represent the state of the art in biopharmaceutical process characterization. However, such methods alone do not leverage the fact that processes operate as a mutual interplay of multiple steps. Instead, they aim to investigate only one process step at a ti...

Integrated or holistic process models may serve as the engine of a digital asset in a multistep-process digital twin. Concatenated individual-unit operation models are effective at propagating errors over an entire process, but are nonetheless limited in certain aspects of recent applications that prevent their deployment as a plausible digital ass...

Intermediate acceptance criteria are the foundation for developing control strategies in process validation stage 1 in the pharmaceutical industry. At drug substance or product level such intermediate acceptance criteria for quality are available and referred to as specification limits. However, it often remains a challenge to define acceptance cri...

Shake flasks remain one of the most widely used cultivation systems in biotechnology, especially for process development (cell line and parameter screening). This can be justified by their ease of use as well as their low investment and running costs. A disadvantage, however, is that cultivations in shake flasks are black box processes with reduced...

Residual process brine is a sustainable raw material for chlor-alkali electrolysis processes. This study investigates the influence of critical process parameters on the performance of a continuous treatment process for residual process brine using halophilic microorganisms. The goal of the bioprocess is an efficient degradation of the organic impu...

Partial least squares (PLS) regression enjoys great popularity as a multivariate regression method that is relatively easy to use while at the same time offering a high level of interpretability. These traits make PLS especially useful for the analysis of spectroscopic measurements in industries with stringent quality standards such as the (bio-) p...

Integrating bioprocess solutions for treatment and subsequent reuse of saline residual process brine into industrial processes could increase the sustainability of production chains. However, such bioprocesses require large-scales and a robust operation over a prolonged period. Consequently, the aim of this study was to analyze scale-up equivalence...

(1) Background: The N-glycosylation profile as well as the subunit assembly of monoclonal antibodies (mAbs) are strongly dependent on manufacturing conditions and thus need to be monitored during the bioprocess. Commonly, mAbs are characterized downstream of the fermentation process applying different analytical techniques like released glycan anal...

In this study, continuous cultivations of C. carboxidivorans to study heterotrophic and mixotrophic conversion of glucose and H2, CO2, and CO were established. Glucose fermentations at pH 6 showed a high ratio of alcohol-to-acid production of 2.79 mol mol⁻¹. While H2 or CO2 were not utilized together with glucose, CO feeding drastically increased t...

• simple unstructured process model of E. coli, describing product formation kinetics and metabolic load, valid for different feeding regimes • nonlinear control law obtained by nonlinear feedback linearization to directly control the specific productivity by the glycerol feed • two-degrees-of-freedom control implementation and stability testing...

Microbial systems play a fundamental role in all parts of biotechnology in a multitude of industrially used processes. Continuous cultivations are referred to increase the time–space yield (TSY) of many processes and provide optimal usage of installed assets. More important than batch definition is the application of the quality-by-design context t...

Mechanistic model-based methods are indispensable tools for characterization, monitoring and control in biopharmaceutical industry. However, the complexity of mechanistic models is restricted by the availability of process analytics. As a result, biological reactions are often lumped and only central metabolic pathways and extracellular analytics a...

Laboratory automation that drives integrated miniaturized and parallel reactor systems incorporating analytical devices for online reaction monitoring has reached a remarkable level of sophistication. The result is a significant increase in experimental throughput allowing the generation of large amounts of data under complex experimental settings...

Monitoring and control of biological processes is still mainly limited to only a few physical and chemical properties that can be measured online with relatively low efforts. Important parameters and variables of a bioprocess are predominantly determined by offline sampling as they are diffi-cult to accurately measure online. Therefore closed-loop...

Process monitoring in microbial cultures became feasible thanks to the development of accurate measurement devices, including in-situ probes to monitor biomass growth, oxygen, carbon dioxide and sugar consumption. In comparison, estimating the metabolic fluxes of the cell factories still rely on analysis based on an under-determined set of equation...

In addition to often reported control of the specific growth rate we show in this contribution a novel method to control the biomass specific substrate uptake as well as the protein production rate during the production phase of microbial fed-batch cultures. The control laws base on a calibrated process model including experimental data sets with d...

Simplicity renders shake flasks ideal for strain selection and substrate optimization in biotechnology. Uncertainty during initial experiments may, however, cause adverse growth conditions and mislead conclusions. Using growth models for online predictions of future biomass (BM) and the arrival of critical events like low dissolved oxygen (DO) leve...

Model-based state estimators enable online monitoring of bioprocesses and, thereby, quantitative process understanding during running operations. During prolonged continuous bioprocesses strain physiology is affected by selection pressure. This can cause time-variable metabolic capacities that lead to a considerable model-plant mismatch reducing mo...

During process development, bioprocess data need to be converted into applicable knowledge. Therefore, it is crucial to evaluate the obtained data under the usage of transparent and reliable data reduction and correlation techniques. Within this contribution, we show a generic Monte Carlo error propagation and regression approach applied to two dif...

Maximizing the value of each available data point in bioprocess development is essential in order to reduce the time-to-market, lower the number of expensive wet-lab experiments, and maximize process understanding. Advanced in silico methods are increasingly being investigated to accomplish these goals. Within this contribution, we propose a novel...

Bacteriocins are antimicrobial peptides produced by bacteria to inhibit competitors in their natural environments. Some of these peptides have emerged as commercial food preservatives and, due to the rapid increase in antibiotic resistant bacteria, are also discussed as interesting alternatives to antibiotics for therapeutic purposes. Currently, co...

In many industrial sectors continuous processing is already the golden standard to maximize productivity. However, when working with living cells, subpopulation formation causes instabilities in long-term cultivations. In cascaded continuous cultivation, biomass formation and recombinant protein expression can be spatially separated. This cultivati...

Predicting the fate of individual cells among a microbial population (i.e., growth, gene expression) remains a challenge, especially when this population is exposed to very dynamic environmental conditions, such as those encountered during continuous cultivation. Indeed, the dynamic nature of a continuous cultivation process implies the potential d...

Current trends in the biopharmaceutical market such as the diversification of therapies as well as the increasing time-to-market pressure will trigger the rethinking of bioprocess development and production approaches. Thereby, the importance of development time and manufacturing costs will increase, especially for microbial production. In the pres...

Bioreactors are essential tools for the development of efficient and high-quality cell therapy products. However, their application is far from full potential, holding several challenges when reconciling the complex biology of the cells to be expanded with the need for a manufacturing process that is able to control cell growth and functionality to...

Predicting the fate of a microbial population (i.e., growth, gene expression…) remains a challenge, especially when this population is exposed to very dynamic environmental conditions, such as those encountered during continuous cultivation. Indeed, the dynamic nature of continuous cultivation process implies the potential deviation of the microbia...

Overexpression of recombinant proteins in Escherichia coli results in misfolded and non-active protein aggregates in the cytoplasm, so-called inclusion bodies (IB). In recent years, a change in the mindset regarding IBs could be observed: IBs are no longer considered an unwanted waste product, but a valid alternative to produce a product with high...

Saline wastewater contaminated with aromatic compounds can be frequently found in various industrial sectors. Those compounds need to be degraded before reuse of wastewater in other process steps or release to the environment. Halophiles have been reported to efficiently degrade aromatics, but their application to treat industrial wastewater is rar...

In this study the use of a particle filter algorithm to monitor Corynebacterium glutamicum fed-batch bioprocesses with uncertain raw material input composition is shown. The designed monitoring system consists of a dynamic model describing biomass growth on spent sulfite liquor. Based on particle filtering, model simulations are aligned with contin...

Predicting the fate of a microbial population (i.e., growth, gene expression) remains a challenge, especially when this population is exposed to very dynamic environmental conditions, such as those encountered during continuous cultivation processes. Indeed, the dynamic nature of continuous cultivation process implies the potential deviation of the...

New possibilities for sustainable and climate-friendly plastic production are urgently needed. One degradable alternative could be polyhydroxybutyrate naturally produced out of CO2 via photosynthesis within cyanobacteria. Therefore, the polyhydroxybutyrate production of the so far little investigated polyhydroxybutyrate overproducing Synecho-cystis...

The use of autosamplers connected to high throughput analytical devices allows for a high sampling frequency and analytics with reduced manual labor, leading to better process characterization (Maurer et al., 2015; Hofer et al., 2020). Increased sampling often leads to a significantly increased information content in the generated data. However, in...

Digital methods for process design, monitoring, and control can convert classical trial-and-error bioprocess development to a quantitative engineering approach. By interconnecting hardware, software, data, and humans currently untapped process optimization potential can be accessed. The key component within such a framework is a digital twin intera...

Recombinant protein production with Escherichia coli is usually carried out in fed-batch mode in industry. As setup and cleaning of equipment are time-and cost-intensive, it would be economically and environmentally favorable to reduce the number of these procedures. Switching from fed-batch to continuous biomanufacturing with microbials is not yet...

A Process characterization is a regulatory imperative for process validation within the biopharmaceutical industry. Several individual steps must be conducted to achieve the final control strategy. For that purpose, tools from the Quality by Design (QbD) toolbox are often considered. These tools require process knowledge to conduct the associated d...

Continuous bioprocesses are widely used for quantitative strain characterization and industrial fermentations aiming for high space time yields and constant productivity. However, due to the presence of different biochemical reaction dynamics these processes can exhibit slow system behavior under certain conditions. This leads to extended start up...

Off-gas measurements give valuable information on the respiratory activity of organisms during fermentation processes. Measured oxygen consumption and carbon dioxide production is usually linked to the overall metabolic activity of the cultivated cells. Together with offline measured nutrient and metabolite concentrations reaction parameters of gro...

Continuous cultivation with Escherichia coli has several benefits compared to classical fed-batch cultivation. The economic benefits would be a stable process, which leads to time independent quality of the product, and hence ease the downstream process. However, continuous biomanufacturing with E. coli is known to exhibit a drop of productivity af...

With increasing bioreactor volumes, the mixing time of the reactor increases as well, which creates an inhomogeneous environment for the cells. This can result in impaired process performance in large‐scale production reactors. Particularly the addition of base through the reactor headspace can be problematic, since it creates an area, where cells...

Cell morphology of filamentous microorganisms is highly interesting during cultivations as it is often linked to productivity and can be influenced by process conditions. Hence, the characterization of cell morphology is of major importance to improve the understanding of industrial processes with filamentous microorganisms. For this purpose, relia...

Process monitoring is a critical task in ensuring the consistent quality of the final drug product in biopharmaceutical formulation, fill, and finish (FFF) processes. Data generated during FFF monitoring includes multiple time series and high-dimensional data, which is typically investigated in a limited way and rarely examined with multivariate da...

Biopharmaceutical drug substances are generally produced using fermentation technology and are subsequently purified in the following downstream process. For the determination of critical quality attributes (CQAs), such as target protein titer and purity, monitoring tools are required before quality control analysis. We herein present a novel rever...

The bacterium E. coli is one of the most important hosts for recombinant protein production. The benefits are high growth rates, inexpensive media, and high protein titers. However, complex proteins with high molecular weight and many disulfide bonds are expressed as inclusion bodies (IBs). In the last decade, the overall perception of these IBs be...

Timely monitoring and control of critical process parameters and product attributes are still the basic tasks in bioprocess development. The current trend of automation and digitization in bioprocess technology targets an improvement of these tasks by reducing human error and increasing through-put. The gaps in such automation procedures are still...

Large‐scale bioreactors for the production of monoclonal antibodies reach volumes of up to 25 000 L. With increasing bioreactor size, mixing is however affected negatively, resulting in the formation of gradients throughout the reactor. These gradients can adversely affect process performance at large scale. Since mammalian cells are sensitive to c...

Monitoring process variables in bioprocesses with complex expression systems, such as filamentous fungi, requires a vast number of offline methods or sophisticated inline sensors. In this respect, cell viability is a crucial process variable determining the overall process performance. Thus, fast and precise tools for identification of key process...

The competitiveness of the chemical and pharmaceutical industry is based on ensuring the required product quality while makingoptimum use of plants, raw materials, and energy. In this context, effective process control using reliable chemical processanalytics secures global competitiveness. The setup of those control strategies often originate in p...

Complex processes meet and need Industry 4.0 capabilities. Shorter product cycles, flexible production needs, and direct assessment of product quality attributes and raw material attributes call for an increased need of new process analytical technologies (PAT) concepts. While individual PAT tools may be available since decades, we need holistic co...

Complex processes meet and need Industry 4.0 capabilities. Shorter product cycles, flexible production needs, and direct assessment of product quality attributes and raw material attributes call for an increased need of new process analytical technologies (PAT) concepts. While individual PAT tools may be available since decades, we need holistic co...

Background: Biomass growth of Pencillium chrysogenum is characterised by a distinct pellet morphology consisting of compact hyphal agglomerates. Fungal pellets are advantageous in industrial process control due to rheological advantages but lead to biomass degradation due to diffusional limitations of oxygen and substrate in the pellet's core. Sev...

Assessment of viable biomass is challenging in bioprocesses involving complex media with distinct biomass and media particle populations. Biomass monitoring in these circumstances usually requires elaborate offline methods or sophisticated inline sensors. Reliable monitoring tools in an at-line capacity represent a promising alternative but are sti...

During the scale‐up of a bioprocess, not all characteristics of the process can be kept constant throughout the different scales. This typically results in increased mixing times with increasing reactor volumes. The poor mixing leads in turn to the formation of concentration gradients throughout the reactor and exposes cells to varying external con...

Process models, consisting of transferable and applicable knowledge, can be used for various tasks such as process development and optimization, and for predicting and controlling critical process variables. In this regard, mechanistic process models, describing the mechanism of a system with a distinct model structure and characteristic parameters...

Risk assessments (RAs) are frequently conducted to assess the potential effect of process parameters (PPs) on product quality attributes (e.g., a critical quality attribute (CQA)). To evaluate the PPs criticality the risk priority number (RPN) for each PP is often calculated. This number is generated by the multiplication of three factors: severity...

Real-time measurements and adjustments of critical process parameters are essential for the precise control of fermentation processes and thus for increasing both quality and yield of the desired product. However, the measurement of some crucial process parameters such as biomass, product, and product precursor concentrations usually requires time-...

Continuous bioprocessing using cell retention allows the achievement of high space-time yields for slow-growing organisms such as halophiles. However, the lack of efficient methods for monitoring and control limits the application of biotechnological processes in the industry. The aim of this study was to implement a control and online monitoring s...

Real-time information on biomass concentration is of critical importance for robust control of any bioprocess. In this application report, C01 and 0, off gas concentrations measured by BlueSens gas analyzer technology were used to accurately estimate biomass concentrations during a Penicillium chrysogenum fed-batch process. The estimation method is...

Conventional polymers are made from fossil resources and consume fossil energy in their production, yielding CO 2 emissions. Production of large-volume compounds from CO 2 , either from point sources or from the air, could reduce anthropogenic global warming. Poly(3-hydroxy-butyrate) (PHB) is a biodegradable and biobased thermoplastic polymer which...

Escherichia coli still serves as a beloved workhorse for the production of many biopharmaceuticals as it fulfills essential criteria, such as having fast doubling times, exhibiting a low risk of contamination, and being easy to upscale. Most industrial processes in E. coli are carried out in fed-batch mode. However, recent trends show that the biot...

Abstract Within this work a nonlinear model predictive controller (MPC) was implemented in a Penicillium chrysogenum fed-batch process and compared to a PI(D) and an open loop feedback control scheme, referenced as model based control (MBC). The controllers were used to maintain predefined set-points of biomass specific glucose uptake rates, prod...